The present invention relates generally to the dental industry and, more particularly, to dental tools which are used in the production of dental cast models.
In the dental industry, technicians commonly construct dental models. A dental model of the entire mouth of a patient typically comprises an upper jaw model and a lower jaw model which are affixed to one another by an articulator. An articulator is a device comprising upper and lower mounting platforms which are connected to the upper and lower jaw model elements. The articulator enables for centric, lateral and protrusive movement of the upper jaw model relative to the lower jaw model in order to closely simulate the relationships and the actual movement, or bite, of the mouth of the patient.
Various types of devices and procedures have been used in the art for creating dental models.
One method for manufacturing dental models which is well known and commonly used in the art involves molding the dental model using a casting material. Specifically, one or more impression trays are filled with rubber based impression material. Each impression tray is then urged into the mouth of the patient so as to create a negative impression of the teeth of the patient into the rubber based impression material. If necessary, excess impression material is trimmed from the impression tray after the negative impression is formed.
After the negative impression has been formed, the impression tray is typically transported to a dental laboratory where the dental cast model is manufactured. Specifically, the negative impression created in the impression tray is filled with a soft casting material, such as dental stone, plaster or epoxy. The impression tray is then inverted and mounted upon a pre-formed mounting device, such as a dental cast tray or base. After the casting material has had an opportunity to harden, the impression tray is removed so that the casting material forms a positive dental impression on the mounting surface.
Molded dental models are often used to manufacture crowns, bridges, inlays, dentures and other dental prosthetics outside of the mouth of the patient. The construction of dental prosthetics typically necessitates the ability to remove one or more individual model teeth from its spatial physical relationship relative to the remainder of the dental cast model for the purpose of constructing accurate margins and contours. In the event that two or more individual units of bridgework are to be joined, it is necessary that the working model segments be accurately and repeatedly returned to their original relationships precisely as they existed prior to any cutting, separations or disassembly of the model.
In order to effectively remove an individual model segment from the remainder of the dental model, the entire jaw model is typically removed from the mounting device and positioned upon a flat cutting surface, such as a table. A cutting device, such as a saw, can then be used to separate the desired model teeth from the remainder of the dental model. After the technician has completed manufacture of the dental work, the dental model can be re-assembled onto the mounting device.
It should be noted that during the re-assembly of the dental cast model, it is essential that precise registration and desired alignment be maintained between the working model segments and the remainder of the molded dental cast model.
In U.S. Pat. No. 5,393,227 to W. H. Nooning, there is disclosed a dental impression handling tool consisting of two base structures shaped to approximate two opposite quadrants of a full dental arch, and two similarly-shaped inserts that snap fit into the base structures. Each base includes a wide, upward facing trough approximating the placement and curvature of teeth within a dental quadrant. The upper surface of each insert is attached to a positive dental mold by means of protrusions that extend from the top horizontal surface of the insert, the protrusions being encased within the mold material. Positive positional relationship is maintained between each base and its mating insert by the use of an interlocking and non-recurring geometric pattern that is carried by the internal vertical walls of the trough in the base, and by a matching geometric pattern that is carried by the outer vertical walls of two vertically downward extending ribs on the underside of the insert. A second deeper, narrow and centrally located trough is formed in each base. This second trough mates with a third center rib that protrudes from the bottom surface of each insert. The insert""s center rib contains a retainer bead along both vertical side walls. This bead provides a snap-lock fit into a corresponding negative indentation formed along the vertical side walls of the center trough of in each base. The center rib in each insert contains cylindrical cavities which allow the insertion of standard dental dowels or suitable substitutes.
Dental impression handling tools of the type described above in Nooning have been found to be experience numerous drawbacks
As a first drawback, dental impression handling tools of the type described above in Nooning are undesirable in that the base comprises an elongated slot into which debris, such as plaster, can collect. As a result, it has been found that the insert is often unable to secure a proper fit within the base structure, thereby precluding proper alignment, which is highly undesirable.
As a second drawback, dental impression handling tools of the type described in Nooning are undesirable in that the bottom surface of the each insert includes various sized ribs, thereby creating a bottom surface which is highly unstable. As a result, when the insert is placed upon a laboratory table in order to cut the desired model teeth from the remainder of the dental cast model, the non-flat and unstable nature of the bottom surface of each insert renders the cutting process extremely difficult, which is highly undesirable.
Accordingly, in U.S. Pat. No. 6,106,284 to R. J. Cronin et al., there is disclosed, in one embodiment, a dental cast tray assembly used to form a dental cast model which comprises a base and a tray removably mounted on the base. The base includes a top surface, a flat bottom surface, a front wall, a rear wall and a plurality of projections formed on its top surface in a non-recurring, random pattern. Each of the plurality of projections is generally cylindrically-shaped and includes a convex free end. The tray includes a top surface adapted to support the dental cast model, a flat bottom surface, a front wall, a rear wall, a retention bar formed on its top surface and a plurality of openings formed in its bottom surface in the same non-recurring, random pattern in which the plurality of projections are disposed on the base. Each of the plurality of openings is defined by four sidewalls and is generally hourglass shaped in lateral cross-section. Two of the four sidewalls which define each of the plurality of openings include an elongated rib. In use, the tray is mounted on the base such that the bottom surface of the tray abuts against the top surface of the base and so that the front wall of the tray is flush with the front wall of the base. With the tray mounted on the base, one projection in the base projects into an associated opening in the tray, the elongated ribs serving to retain each projection within its associated opening with limited retention.
Although highly effective in constructing a dental cast model, the dental cast tray assembly described in Cronin et al. suffers from some notable drawbacks.
As a first drawback, it has been found that the dental cast tray assembly described in Cronin et al. is difficult to manufacture due to the T-shape of the retainer bar. Specifically, the undercuts of the T-shaped retainer bar are difficult to create using conventional molding processes, thereby increasing the overall cost to manufacture the dental cast tray assembly, which is undesirable.
As a second drawback, it has been found that the dental cast tray assembly described in Cronin et al. is difficult to manufacture due to the particular arrangement of posts on the base and openings in the tray. Specifically, the exactness required in constructing each of the plurality of posts on the base to fit snugly within an associated opening in the tray significantly complicates the molding process, thereby increasing the overall cost to manufacture the dental cast tray assembly, which is undesirable.
As a third drawback, it has been found that the dental cast tray assembly described in Cronin et al. often requires considerable clean-up. Specifically, in use, casting material is spread both within the negative impression of the impression tray and onto the top surface of the tray around the retention bar. However, it has been found that, before the casting material has had a chance to harden, some of the casting material often drips off of the top surface of the tray and onto the base and working table. As a result, the dental technician is often required to spend a considerable amount of time and energy to clean-up the excess casting material which accumulates on the base and the working surface, which is undesirable.
As a fourth drawback, it has been found that the dental cast tray assembly described in Cronin et al. is often difficult to use. Specifically, in use, casting material is spread both within the negative impression of the impression tray and onto the top surface of the tray around the retention bar. However, it has been found that the application of the casting material around the entire retention bar is often difficult to achieve due to the undercuts of the T-shaped retention bar. As a result, if the casting material is not properly spread around the entire retaining bar, air gaps can form between the plaster and the tray, thereby weakening the strength of the retention of the dental cast model on the tray, which is undesirable.
As a fifth drawback, it has been found that the tray and base of the dental cast tray assembly described in Cronin et al. are difficult to mount together. Specifically, each of the large quantity of posts on the base must be properly aligned and inserted into an associated opening in the tray. As a result, a considerable amount of dexterity is required to ensure that each post projects within an associated opening, which is undesirable. In addition, due to the large quantity of posts and openings, a considerable amount of retentive force must be overcome in order to advance each post into its associated opening, which is undesirable.
As a sixth drawback, it has been found that the tray and base of the dental cast tray assembly described in Cronin et al. are difficult to separate. Specifically, the large number of posts and openings creates a significant retentive force between the base and the tray which is difficult to overcome, which is undesirable. Furthermore, because the tray lies flush on top of the base, the user is incapable of wedging an object between the base and the tray to facilitate separation, which is undesirable.
As a seventh drawback, it has been found that the dental cast tray assembly described in Cronin et al. does not indicate to the user whether the tray is adequately mounted onto the base. Specifically, the user is often unaware if the tray has been properly mounted on the base such that each projection extends completely into its associated openings, which is undesirable.
It is an object of the present invention to provide a new and improved dental cast tray assembly which can be used to produce a dental cast model.
It is another object of the present invention to provide a dental cast tray assembly as described above which includes a tray on which the dental cast model is mounted.
It is yet another object of the present invention to provide a dental cast tray assembly as described above which allows for repeated removal and replacement of the tray onto a base with proper alignment.
It is still another object of the present invention to provide a dental cast tray assembly as described above which enables the dental cast model to be easily cut into working segments.
It is another object of the present invention to provide a dental cast tray assembly as described above wherein the tray is constructed to securely retain the dental cast model thereon.
It is still another object of the present invention to provide a dental cast tray assembly as described above which is inexpensive to manufacture, has a minimal number of parts, is limited in size and can be very easily used.
Accordingly, as one feature of the present invention, there is provided a dental cast tray assembly for forming a dental cast model, comprising a base having an elongated projection, and a tray removably mounted on said base, said tray being adapted to support the dental cast model, said tray including an elongated opening, wherein said projection is sized and shaped to releasably fit into the opening in said tray.
As another feature of the present invention, there is provided a dental cast tray assembly for forming a dental cast model, comprising a base, and a tray removably mounted on said base, said tray being adapted to support the dental cast model, wherein, with said tray mounted on said base, said dental cast tray assembly is shaped to include a slot at the junction between said base and said tray for assisting in the removal of said tray from said base.
Additional objects, as well as features and advantages, of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration an embodiment for practicing the invention. The embodiment will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.